The present invention relates in general to a sewing machine and, in particular, to a new and useful means for attaching or detaching a presser foot shoe to or from a connecting member to which a presser bar is connected.
Two types of presser feet for sewing machines are known. A presser foot of one of the two types is directly attached to a presser bar with a set screw. In this arrangement, the presser foot must be made of similar material as the bar so as to possess like strength and, moreover, accuracy is required to minimize errors in the dimensions of the foot and bar.
Presser feet of the other type are shown in FIGS. 1 and 2, for example. Both consists of a shank a and a presser foot shoe b detachably joined to each other. Shank a has a slot 1 provided at its bottom while presser foot shoe b has a pair of supports or forks 2 (only one is shown in part) provided on its upper surface at opposite sides of shoe b. A shaft 3 is received in openings of both supports 2.
In order to connect shank a to presser foot shoe b, in the case of FIG. 1, shaft 3 is inserted in slot 1 whereon slot 1 is closed with the end of a horizontal portion of an L-shaped leaf spring 4, which is tightly fitted along the bottom of shank a and up along the rear wall of shank a with the upper end of leaf spring 4 fixed to shank a. Spring 4 thus engages shaft 3 between forks 2.
Slot 1 is opened by pulling leaf spring 4 with a lever 5 as shown in a dash-dot line position in FIG. 1.
Alternatively, as shown in FIG. 2, shank a is connected to presser foot shoe b by means of a lever 6 which is pivotally connected to shank a such that a claw-like end 6d of lever 6 is spring-biased by a spring 6a so as to urge shaft 3 against slot 1.
Accurate machining is thus necessary to form a clearance c between the bottom surface of shank a and the upper surface of presser foot shoe b. These conventional presser feet, therefore, rendered manufacturing complicated and costly so that they are not generally suitable for practical use.